A common misconception is that rain causes windows to dirty and spot.  Not true.

As discussed and dispelled in Good Housekeeping and Martha Stewart Living magazines, rain does not cause windows to dirty/spot.

IF there was even a remote degree of truth to this, unless you lived in Arizona or Nevada, you would never have your glass cleaned!

Rain hitting dirty screens, dirty frames, and/or dirty sills causes windows to become dirty.  Thats what collects dirt.

Additionally, we use a solution that repels spotting.  Most window clients will see their windows still looking crystal sharp after 30-50 significant weather events. 

Test this by looking at two windows. One covered from the rain by an awning perhaps and another that is exposed to weather and rain (after being professionally cleaned).  The window exposed to the rain will remain clean and crisp while the window sheltered from rain will dirty significantly faster.

Cleaning windows in a light, non-driving, rain does not affect the quality of window cleaning whatsoever.  When lightning is present however, we retreat from our ladders.  Ladders and Lightning don't mix.  Usually thunderstorms are short lived though and we will do interior while the storm cell passes.  We do a good job of monitoring radar as well as future radar to stay abreast of any concerns.  (It's amazing the information that one can receive on a smartphone!)

Most homes have overhangs blocking precipitation.

If there is inclement weather on your appointment day, we will respect your time and arrive and do interior work. We will then return within 48 hours to complete exterior work when no one necessarily needs to be home as we will not have to gain entry.  In this way, we respect your busy schedule.